Definition of feldspar in English:


(also felspar)


  • [mass noun] An abundant rock-forming mineral typically occurring as colourless or pale-coloured crystals and consisting of aluminosilicates of potassium, sodium, and calcium.

    • ‘Quartz is associated most commonly with aegirine and potassium feldspar as well as zircon.’
    • ‘Larger crystals of feldspar and quartz dominate the host rock.’
    • ‘Its most abundant mineral is feldspar, which accounts for two-thirds of the Earth's crust.’
    • ‘These granite dikes are composed almost totally of potassium feldspar and quartz.’
    • ‘Minerals such as feldspar, which are insoluble in water, will not give a positive test.’


Mid 18th century: alteration of German Feldspat, Feldspath, from Feld field + Spat, Spath spar (see spar). The form felspar is by mistaken association with German Fels rock.